Assessment of the extremity exposure during preparation and administration of¹⁷⁷Lu - results of a multi-center study

Despite the increased use of¹⁷⁷Lu in nuclear medicine (NM) over the last 10 years, the knowledge of the actual exposure of the extremities due to manipulation of this pharmaceutical is limited. The purpose of this study is to assess the extremity dose during the preparation and administration of¹⁷⁷Lu-labelled radiopharmaceuticals in a wide range of NM practices. Workers in 10 NM centres throughout Europe wore a ring dosimeter on the base of the index finger of the non-dominant hand during preparation and/or administration of¹⁷⁷Lu-labelled radiopharmaceuticals. Information on manipulated activity, tasks performed and protection measures was collected to allow sub-analyses. The median ring dose per monitoring interval was 0.16 mSv, with a maximum of 2.27 mSv in one month. The median normalised dose amounted 3.5µSv GBq^-1(range 0.5-525). The highest monthly doses were found for workers involved in preparation of the pharmaceutical. The workers performing manual administrations (6.5µSv GBq^-1) showed higher normalised ring doses than those using the gravity method (3.5µSv GBq^-1) or a syringe pump (1.0µSv GBq^-1). Explanations for the wide range of normalised ring doses may be found in the different techniques applied in this study and the differences in minimum reportable doses of the dosimeters. When the data is extrapolated using a fingertip to ring dose ratio of 5, an annual fingertip dose of 1-136 mSv is found, with a median fingertip dose of 10 mSv per year. Extremity exposure during¹⁷⁷Lu handling remained well below dose limits. The highest normalised doses occurred during preparation and manual administration. Overall, this investigation shows doses remain low when appropriate radiation protection measures (e.g. shielding and minimising time at short distance) are being applied.